1. Field of the Invention
The present invention concerns management of disk operations, and, more particularly, concerns management of disk operations according to priorities.
2. Related Art
State of the art disk storage systems automatically reorder input/output operations to more nearly optimize disk utilization. To influence or even entirely override this automatic reordering, operations of special importance can be specified via existing disk protocols, such as protocols for tag command queuing. For example, a “head of queue” tag can be used to force a disk array to process an operation ahead of all others. An “order queue” tag can be used to force the disk array to process a particular operation immediately after finishing prior operations. However, this command queuing capability has limitations that tend to restrict its application. Its use tends to be counterproductive when used under ordinary production conditions instead of handling emergencies, such as failover. That is, externally imposed prioritization tends to disrupt automatic optimization. Therefore a more generalized ability is needed to organize disk operations based on priority for ordinary production conditions.